Process and apparatus for producing iron carbide

ABSTRACT

Iron carbide is produced by an apparatus comprising first fluidized bed reactor  4  and second fluidized bed reactor  5 , wherein the charged grainy iron oxide is reduced and carburized by the high temperature and high pressure gas being introduced from the bottom of the reactor. Both fluidized bed reactors comprise chamber  23  for introducing gas into the reactor, distribution plate  27  having multiple gas-introducing nozzles  28 , partition plate  26  partitioning the fluidized bed into plural division rooms, and gas supply inlet  25   a,    25   b  arranged on chamber  23  for supplying gas to specific division room respectively. Each gas supply inlet is connected to gas supply line having a gas flow control valve for controlling gas pressure or gas flow rate.

TECHNICAL FIELD

The present invention relates to a process and apparatus for producingiron carbide.

BACKGROUND ART

A traditional method for producing steel from iron oxide such as ironore normally comprises the steps of;

in the first step, producing molten pig iron in such a manner that cokeproduced at a coke oven, other raw materials and iron oxide are chargedinto a blast furnace, and thereafter, iron oxide are molten and reducedby combustion heat of carbon contained in coke generated due to blowingof high temperature oxygen and carbon monoxide generated due tocombustion of said carbon;

in the second step, charging the molten pig iron into a converter, andconverting the molten pig iron by oxygen blowing into steel, wherein acarbon concentration of which is under the demanded value.

Since such traditional steel making process by a blast furnace requiresmany ancillary facilities such as coke oven, sintering furnace, andair-heating furnace, equipment cost becomes high. Furthermore, thissteel making process via a blast furnace requires the expensive coalsuch as high coking coal and huge site for many facilities and rawmaterials storage. Therefore, recently, to overcome the abovedisadvantages of using a blast furnace, new iron making processes,instead of a blast furnace, have been developed and put to practicaluse.

For example, one of the newly developed processes for producing steel isa method called as iron carbide-electric furnace process. This processcomprises the steps of obtaining iron carbide by reacting grainy ironoxide with a reducing agent such as hydrogen and a carburizing agentsuch as methane gas, and producing steel by smelting said iron carbideat an electric furnace. A fluidized bed reactor is a well knownapparatus for producing iron carbide. The laid open publication No. HEI6-501983, which is the publication of the Japanese translation ofInternational Patent Application No. PCT/US91/05198 discloses anapparatus for producing iron carbide. As shown in FIG. 8, saidpublication shows an apparatus for producing iron carbide, wherein whena grainy iron oxide is charged into fluidized bed reactor 32 via inlet31, the grainy iron oxide is reduced under floating and fluidizing dueto the high temperature and high pressure gas being introduced frommultiple nozzles 33 located in the bottom portion of the reactor.Thereafter, the iron oxide is broken into smaller pieces as a result ofthe foregoing reaction and moves along with a passage formed bybaffle-plates 34, 35, 36, 37, and is finally discharged as iron carbidefrom outlet 38. (Hereinafter, this apparatus is called as prior art.)

By the way, the reaction for converting iron oxide into iron carbideproceeds as shown in the following formulas (1) through (6).

(1) Fe₂O₃+3H₂→2Fe+3H₂O (FeO_(1.5)+1.5H₂→Fe+1.5H₂O)

(2) Fe₃O₄+4H₂→3Fe+4H₂O (FeO_(1.3)+1.3H₂→Fe+1.3H₂O)

(3) Fe₃O₄+H₂→3FeO+H₂O

(4) FeO+H₂→Fe+H₂O

(5) 3Fe+CH₄→Fe₃C+2H₂

(6) 3Fe₂O₃+5H₂+2CH₄→2Fe₃C+9H₂O

As shown in the above formulas (1) through (6), the iron oxide isconverted into iron carbide in turn of Fe₂O₃, Fe₃O₄, FeO, Fe and Fe₃C,and the volume of the reducing gas H₂ to be used varies according toeach stage in the reducing reaction. On the other hand, under some gastemperature or some gas composition, there is such a case that FeO isnot generated. As is described below, the prior art has the variousproblems to be solved.

First, the higher the concentration of methane and carbon monoxidecontained in the reducing and carburizing gas becomes, the faster thecarburizing reaction proceeds. But when the concentration of methane andcarbon monoxide contained in said reaction gas becomes excessively high,a fixed carbon is generated from the reaction gas due to the reaction asshown in the following formulas (7) and/or (8).

As a result, extra reaction gas is uselessly consumed. Furthermore, thefixed carbon has such a bad effect upon the gas circulation loop as tobe turned into dust and sticked on a tube of gas heater.

(7) CH₄→C(fixed carbon)+2H₂

(8) 2CO→C(fixed carbon)+CO₂

At the most vigorous stage of the reaction, the reducing reaction byhydrogen is conducted vigorously as is described above, and the watervapor generated by said reducing reaction prevent the generation offixed carbon. But, at the final stage of the reaction, since littlewater vapor for preventing the generation of fixed carbon is generated,the fixed carbon is liable to easily generate. There are two means toprevent the generation of fixed carbon. One is to decrease theconcentration of methane and carbon monoxide contained in the reactiongas, and the other is to increase the concentration of water vaporcontained in the reaction gas. But those means result in the decline ofthe reaction speed, namely, the lowering of the productivity.

The higher the gas temperature becomes, the faster the reaction speedbecomes. But, when the temperature of the fluidized bed comes to be overabout 600° C. (for example, 570° C.˜590° C.) due to the excessively hightemperature gas, the iron oxide remained in the product of iron carbideis turned into not Fe₃O₄ whose chemical character is stable, but FeOwhose chemical character is unstable.

If the reaction gas temperature is decreased so as to avoid the abovedisadvantage, it will result in the decline of the reaction speed,namely, the lowering of the productivity.

Furthermore, as the reaction proceeds, the specific gravity of ironoxide becomes lower and the diameter of iron oxide particles becomesmaller due to its own powdering. Therefore, the iron oxide particles atthe stage of the second half of the reaction is liable to fly. The ironoxide particles flown outside the reactor has the low carburizationdegree because of the short staying time at the reactor. As a result, itbrings the lowering of the average carburization degree of the productof iron carbide.

Consequently, it is preferable to regulate the flow velocity of the gasflowing through the fluidized bed according to the proceeding of thereaction. But it is impossible for the prior art to change the flowvelocity of the gas, unless applying some complicated works, such asalternating the resistance of the gas blowing nozzle installed at thegas distribution plate.

Furthermore the method for producing iron carbide, which ischaracterized by that the reducing reaction is partially conducted in afirst stage reactor, then the further reducing and carburizing reactionis conducted in a second stage reactor, is known.

But in this method, the control of reduction degree of the oredischarged from the first stage reactor is necessary. It is possible tocontrol the reduction degree by altering the gas flow rate, the gastemperature or the gas composition. Said altering, however, is not easybecause the quantity of gas to deal with is so much. As a result, itpresents the difficulty in controlling conformably and carefully thereduction degree.

The above-mentioned disadvantages of the prior art for producing ironcarbide will be easily overcome by the present invention.

The objective of the present invention is to provide a process andapparatus for producing effectively iron carbide having the chemicallystable components.

DISCLOSURE OF THE INVENTION

An object of this invention is to provide a process for producing ironcarbide by an apparatus having constitution elements (a) to (e);

(a) a fluidized bed located at an upper part within a fludized bedreactor, and,

(b) a chamber located at a lower part within the reactor to work as agas header for introducing a reducing and carburizing gas; wherein thefluidized bed and the chamber are separated into upside and downside bya distribution plate on which multiple gas introducing nozzles areinstalled; and the fluidized bed located at an upper part of thedistribution plate is partitioned into plural division rooms which areformed in isolated or mazy room by a partition plate; and,

(c) plural gas supply inlets arranged on the chamber for supplying gasrespectively to the specific division room, and, connecting a gas supplyline to each gas supply inlet in order to supply a reducing andcarburizing gas, wherein each gas supply line has a gas flow controlvalve which controls gas pressure or gas flow rate; and,

(d) one or more than two of gas circulation loop having a quenchingtower and a cooler which eliminate dusts contained in the exhaust gasand reduce water vapor contained in the exhaust gas, and having apreheater for heating the gas, wherein the exhaust gas is returned tothe chamber by way of the quenching tower, cooler and preheater; and,

(e) a gas supplying apparatus through which hydrogen gas andcarbon-containing gas such as methane are supplied to a gas circulationloop; and further, comprising steps for reacting grainy iron oxidecharged from a side wall of the reactor with the gas in such a mannerthat;

the iron oxide is floated and fluidized by high temperature and highpressure gas being introduced form the bottom portion of the reactor,and then, transferred from the division room of the upstream side to thedivision room of the downstream side via a communication space which maylocate at either upper or lower part of said partition plate, andfinally, produced iron carbide is discharged from the final divisionroom.

Another object of the present invention is to provide a process forproducing iron carbide, wherein a chamber is separated into plural partsby separation plate and each separated part comprises an individual gassupply inlet respectively.

Another object of the present invention is to provide a process forproducing iron carbide, wherein a separation plate is installed at theupper part of the chamber in such a manner that only the upper part ofthe chamber is divided into plural parts by said separation plate.

Another object of the present invention is to provide a process forproducing iron carbide, wherein a separation plate is installed from thetop of the chamber to the bottom thereof for isolating each separationpart.

Another object of the present invention is to provide a process forproducing iron carbide, wherein a separation plate is installed from thetop of the chamber to the bottom thereof for separating the chamber intoplural parts, and the separated parts are communicated each other via anaperture arranged on the separation plate.

Another object of the present invention is to provide a process forproducing iron carbide wherein the amount of water vapor contained inthe gas to be supplied to the division room of the downstream side ismade larger than that contained in the gas to be supplied to thedivision room of the upstream side.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the amount of water vapor contained inthe gas to be supplied to the division room of the downstream side isincreased by supplying water vapor from the outside of the reactor.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the amount of water vapor contained inthe gas to be supplied to the division room of the downstream side isincreased in such a manner that cooling operation of a quenching towerand a cooler in a gas circulation loop is regulated so as to decreasethe amount of removal of water vapor by said quenching tower and saidcooler.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the hydrocarbon gas or the carbonmonoxide gas contained in the gas to be supplied to the division room ofthe downstream side is made smaller than that contained in the gas to besupplied to the division room of the upstream side.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the amount of the hydrocarbon gas or thecarbon monoxide gas contained in the gas to be supplied to the divisionroom of the upstream side is increased by supplying hydrocarbon gas orcarbon monoxide gas from the outside of the reactor more than thatcontained in the gas to be supplied to the division room of thedownstream side.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the gas flow rate per unit area of thegas to be supplied to the division room of the downstream side is madesmaller than that of the gas to be supplied to the division room of theupstream side.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstreamside.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstream sidein such a manner that a low temperature gas is mixed with the gasdischarged from the preheater in the gas circulation loop.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the low temperature gas is a part of thegas to be supplied to a preheater.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the low temperature gas is supplied fromthe outside of the reactor.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the temperature of the fluidized bed inthe division room of the downstream side is made in the range of500˜600° C.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the temperature of the fluidized bed inthe last division room of the downstream side is made in the range of500˜600° C. by decreasing the temperature of only the gas to be suppliedto the last division room of the downstream side.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstream sidein such a manner that oxygen is mixed with the gas to be supplied todivision room of the upstream side, and then, a part of combustible gascontained in said gas is partially burned in order to raise the gastemperature.

Another object of the present invention is to provide a process forproducing iron carbide, wherein the concentration of hydrogen containedin the gas to be supplied to the division room of the upstream side ismade higher than that of hydrogen contained in the gas to be supplied tothe division room of the downstream side.

A still further object of the present invention is to provide a processfor producing iron carbide, wherein the concentration of the hydrogen inthe gas to be supplied to the division room of the upstream side isincreased by supplying hydrogen gas from the outside of the reactor.

Another aspect of this invention is to provide an apparatus forproducing iron carbide comprising the constitution elements (a) to (e);

(a) a fluidized bed located at an upper part within a fludized bedreactor, and,

(b) a chamber located at a lower part within the reactor to work as agas header for introducing a reducing and carburizing gas; wherein thefluidized bed and the chamber are separated into upside and downside bya distribution plate on which multiple gas introducing nozzles areinstalled; and the fluidized bed located at an upper part of thedistribution plate is partitioned into plural division rooms which areformed in isolated or mazy room by partition plate; and,

(c) plural gas supply inlets arranged on the chamber for supplying gasrespectively to the specific division room; and, connecting a gas supplyline to each gas supply inlet in order to supply a reducing andcarburizing gas; wherein each gas supply line has a gas flow controlvalve which controls each gas pressure or gas flow rate; and,

(d) one or more than two of gas circulation loop having a quenchingtower and a cooler which eliminate dusts contained in the exhaust gasand reduce water vapor contained in the exhaust gas, and having apreheater for heating the gas, wherein the exhaust gas is returned tothe chamber by way of the quenching tower, cooler and preheater; and,

(e) a gas supplying apparatus through which hydrogen and carbon-containing gas such as methane are supplied to said gas circulationloop.

H₂, CH₄, CO, CO₂ and H₂O and the like can be used as a reaction gas forthe present invention.

The present process and apparatus for producing iron carbide having theabove constructions demonstrates the following advantages.

That is to say, it can be conducted by the present invention that thegas conditions such as gas temperature, gas flow rate and gascomposition, which is introduced into the fluidized bed of iron oxideparticle inside the reactor, may not make fixed but partially changed.

Consequently, it is possible to lower the concentration of methane andcarbon monoxide and raise the concentration of water vapor contained inthe gas introduced into the division room of the downstream side incomparison with the concentration of those gases contained in gasintroduced into the division room of the upstream side. It thus can beachieved to maintain a high productivity operation under preventing thegeneration of fixed carbon from the reaction gas.

It is possible to lower the gas temperature introduced into the divisionroom of the downstream side in comparison with the gas temperatureintroduced into the division room of the upstream side. It thus can beachieved to maintain a high productivity operation and produce ironcarbide having a small quantity of chemically unstable wustite and alarge quantity of chemically stable magnetite.

Furthermore, it is possible to decrease the gas flow rate introducedinto the division room of the downstream side in comparison with the gasflow rate introduced into the division room of the upstream sideaccording to the decreasing specific gravity and particle diameter inaccordance with the proceeding of the reaction. It thus can be achievedto decrease the iron oxide flown the outside the reactor and produceiron carbide having a high average carburization ratio.

In case of conducting the reducing and carburizing reaction using tworeactors, it is easy to alter the gas flow rate, the gas compositionand/or the gas temperature because the gas quantity introduced into thedivision room of the fluidized bed at the final reaction stage of thefirst reactor is smaller than the whole gas quantity. It thus can easilybe achieved to control the reduction degree of iron oxide includingmetallic iron discharged from the first reactor.

Furthermore, by the present invention, it can be accomplished to preventthe generation of fixed carbon from the reducing and carburizing gas andallow the kind of iron oxide remaining in the product of iron carbide tobe magnetite whose chemical character is stable. It also can beaccomplished to decrease the quantity of iron ore particle flown outsidethe reactor.

As a result, the present invention can provide a process and apparatusfor producing effectively iron carbide with the high operation ratio andthe low production cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram showing example of the entireconstruction of a process for producing iron carbide of the presentinvention.

FIG. 2 shows an example of a supply passage of makeup gas.

FIG. 3 is a figure showing an example of a fluidized bed reactor.

FIG. 3(a) shows a longitudinal sectional view of a fluidized bed reactorwhose fluidized bed is partitioned into two parts

FIG. 3(b) shows a sectional view at the line III—III of FIG. 3(a).

FIG. 4 is a figure showing the change of the amount of water generatedby the reducing reaction of iron oxide during the batch test.

FIG. 5 is a figure showing the change of the amount of hydrogen consumedby the reducing reaction of iron oxide during the batch test.

FIG. 6 is a longitudinal sectional view showing an example of the lowerpart of the fluidized bed reactor of the present invention.

FIG. 7 is a longitudinal sectional view showing an another example ofthe lower part of the fluidized bed reactor of the present invention.

FIG. 8 shows a plan view of an example of conventional fluidized bedreactor.

FIG. 9 shows a sectional view at the line IX—IX of FIG. 8.

BEST MODE FOR CARRYING OUT THE INEVNTION

Hereinafter, the embodiments of a process and apparatus for producingiron carbide in accordance with the present invention is explainedtogether with related drawings.

FIG. 1 is a flow diagram showing the entire construction in case ofapplying the present invention to an apparatus for producing ironcarbide having two reactors (two reactor stages). In FIG. 1, grainy rawmaterials (iron oxide) are charged into an ore dryer 2 as indicated byarrow 1, and said iron oxide is dried in the ore dryer 2 by hightemperature gas introduced from hot gas generator 3, and thereafter,said iron oxide is carried to first fluidized bed reactor 4.

In first fluidized bed reactor 4, the grainy iron oxide is preliminarilyreduced under fluidizing by the reducing gas introduced from the bottomof said reactor. The preliminarily reduced iron oxide is carried tosecond fluidized bed reactor 5. In second fluidized bed reactor 5, thegrainy preliminarily reduced iron oxide is further reduced andcarburized under fluidizing by the reducing and carburizing gasintroduced from the bottom of said reactor, and converted into ironcarbide. The product (iron carbide) is carried to buffer tank 6 a, 6 b,and then, transported to a melting furnace such as an electric furnaceby means of transportation such as a truck via conveyer 7.

FIG. 1 shows cyclone separator 8 a, 8 b, heat exchanger 9 a, 9 b,quenching tower 10 a, 10 b, water chiller 11, cooler 12 a, 12 b,knockout drum 13 a, 13 b which catch a drop of water and discharge itoutside, compressor 14 a, 14 b, and preheater 15 a, 15 b. As shown inFIG. 1, both first fluidized bed reactor 4 and second fluidized bedreactor 5 have the individual gas circulation loop A, B respectively.FIG. 2 illustrates that each gas passage 16 a, 16 b connected to saidgas circulation loop is lead to a supply passage of H₂ gas, CO gas, CO₂gas or natural gas(NG). In FIG. 2, the numeral 17 shows a desulfurizer.Each chamber, where is located at the lower part of first fluidized bedreactor 4 and second fluidized bed reactor 5, has two gas supply inlets(described after in detail) respectively.

Gas supply line 18 a and 18 c are connected to gas supply inlets offirst fluidized bed reactor 4. Gas supply line 18 a is connected to gassupply line 18 b via gas supply line 18 d. Gas supply line 18 f and 18 hare connected to gas supply inlets of second fluidized bed reactor 5.Gas supply line 18 e is connected to gas supply line 18 g via gas supplyline 18 i. Each of gas supply line 18 a, 18 d and 18 b has gas flowcontrol valves 19 a, 19 b and 19 c respectively. Each of gas supply line18 e, 18 i, and 18 g has gas flow control valves 19 d, 19 e, 19 frespectively.

FIG. 3 illustrates the detailed constitution of a first fluidized bedreactor or a second fluidized bed reactor.

Chamber 23 locating beneath fluidized bed 22 is separated into twoisolated parts 23 a, 23 b by separation plate 24 and each part 23 a, 23b has gas supply inlet 25 a, 25 b respectively. Fluidized bed 22 ispartitioned into division room 22 a of the upstream side and divisionroom 22 b of the downstream side by partition plate 26.

Fluidized bed 22 and chamber 23 are separated into upside and downsideby distribution plate 27. Distribution plate 27 has plural nozzles 28for introducing gas. The numeral 29 is an inlet for charging rawmaterials and numeral 30 is an outlet for discharging the product ofiron carbide.

In this fluidized bed reactor, under fluidizing, the charged grainy ironoxide existing in division room 22 a of the upstream side flows overpartition plate 26 and flows into division room 22 b of the downstreamside. It is possible that the temperature, composition and flow rate ofeach gas, which is supplied to parts 23 a and 23 b of chamber 23, may bedifferent each other.

Process for producing iron carbide is described in more detail asfollows using the apparatus having the above mentioned constitution.

Grainy iron oxide dried in ore dryer 2 is carried into first fluidizedbed reactor 4 via passage 20, and is reduced and carburized underfloating and fluidizing by a high temperature (approximately 650° C.)and high pressure (approximately 5 atmospheric pressure) gas beingintroduced from the bottom portion of the reactor. The reducing andcarburizing reaction consumes a large amount of H₂ and CH₄ and generatesa considerable amount of water. Consequently, the gas exhausted at about600° C. from the top of the reactor contains a considerable amount ofwater vapor. This high temperature and large moisture-containing gas iscooled along with passing through the gas circulation loop and watervapor contained in the gas is turned into water, and this water iseliminated. After that, H₂ and CH₄ is supplied to the gas circulationloop. As a result, the reaction in the fluidized bed reactor isexpedited more efficiently.

Cooling and circulation of gas in gas circulation loop A is explained indetail hereinafter:

A reaction gas is cooled according to the following steps;

in the first steps, since a reaction gas discharged from the top of thereactor contains extremely fine particles of iron oxides, a part of fineparticles of iron oxide are acquired by cyclone separation 8 a;

in the second step, a water vapor-containing gas discharged from thereactor at about 600° C. is cooled to 500° C. while going throughpassage 21;

in the third step, the water vapor-containing gas is cooled to about220° C. by heat exchanger 9 a;

in the fourth step, the gas is cooled to about 40° C. while goingthrough quenching tower 10 a to which cool water obtained at coolingtower (not shown) is supplied;

in the fifth step, the gas is cooled to about 20° C. while going throughcooler 12 a to which cool water generated by water chiller 11 issupplied;

in the final step, water content is eliminated from the gas at knockoutdrum 13 a.

The gas cooled to about 20° C. is pressurized by compressor 14 a toabout 5 atmospheric pressure, and heated to about 400° C. by a hightemperature gas discharged from the reactor at heat exchanger 9 a.Further, the gas is returned into fluidized bed reactor 4 after beingheated to about 650° C. at preheater 15 a.

The gas having desirable components is supplied via a gas supply passageas shown in FIG. 2 because the circulating gas is gradually consumedaccording to the proceeding of the reaction in the reactor.

The above mentioned reaction in a gas circulation loop A also takesplace in a gas circulation loop B.

According to the above mentioned process, the iron oxide charged intofirst fluidized bed reactor 4 is converted to iron carbide (Fe₃C) atsecond fluidized bed reactor 5 and said iron carbide is discharged fromthe reactor.

By the way, in components of iron oxide, wustite is chemically unstableand magnetite is chemically stable.

When the temperature of reaction gas is in the range of 500° C. to about600° C., wustite is not generated but magnetite is generated accordingto the equilibrium of Fe—H—O and Fe—C—O.

The iron oxide component, which remains in the product of iron carbide,is preferably magnetite. On the other hand, it is preferable to raisethe temperature of reaction gas more than about 600° C. (for example590° C.) in order to increase the reaction speed. Therefore, in thisembodiment, gas supply line 18 g, which can carry some amount of lowtemperature gas (gas at inlet side of preheater), is connected to line18 h supplying gas to a division room of the downstream side. As aresult, it is possible that the temperature of gas to be supplied to adivision room of the downstream side is controlled in the range of 500°C. to 600° C. and the temperature of the gas to be supplied to adivision room of the upstream side is controlled to be over about 600°C.

As is described above, in the present invention, it is possible that thetemperature of each gas, which is supplied to a division room of theupstream side and a division room of the downstream side, may bedifferent each other. It is also possible to make the gas flow rate andthe gas composition for one division room different from those of theother division room in the same manner.

For example, as shown in FIG. 4 and FIG. 5, since the reducing reactionby hydrogen gas is sufficiently conducted at the mature stage of thereaction, it is desired to make the hydrogen concentration contained ingas to be supplied to a division room of the upstream side larger thanthat contained in gas to be supplied to a division room of thedownstream side.

In accordance with the present invention, even if this reaction isconducted in a single fluidized bed reactor, it is possible to make thehydrogen concentration contained in gas in the upstream side differentfrom that contained in gas in the downstream side by means ofintroducing hydrogen gas into the gas to be supplied to a division roomof the upstream side.

Generally, the high temperature gas containing hydrocarbon such asmethane and carbon monoxide may generate a fixed carbon under a certainconduction. The fixed carbon has the following defects. One of thedefects is that the fixed carbon consumes uselessly the reaction gas.The other defect is that the fixed carbon sticks to equipments such asheater and the like. The another defect is that the fixed carbon invadesinto the material constituting the equipment, and damages said material.The fixed carbon is not generated when a large amount of water iscontained in the gas. In the conventional process for producing ironcarbide, as shown in FIG. 4 and FIG. 5, there is much water in the earlystage of reaction because of the large reducing reaction speed byhydrogen, and the fixed carbon is not easily generated. But, in thefinal stage of reaction, since the reaction speed is low, the watergenerated by the reaction is a little and fixed carbon is liable to begenerated. Consequently, in accordance with the present invention, it ispossible to raise the water concentration contained in gas to besupplied to the division room of the downstream side via line 18 g and18 h by adding steam.

It is preferable to lower the concentration of methane and carbonmonoxide contained in gas in order to prevent the generation of fixedcarbon. But, if the concentration of carbon monoxide and methane islowered, it results in the decrease of the reaction speed, namely, thelowering of the productivity. Therefore, in accordance with the presentinvention, it is possible to lower the concentration of methane andcarbon monoxide contained only in gas of the last division room of thedownstream side by means of restraining the quantity of hydrocarbon andcarbon monoxide to be introduced into gas to be supplied to the lastdivision room of the downstream side.

The specific gravity of iron oxide become lower and the diameter of ironoxide particle become smaller in accordance with the proceeding of thereaction. Therefore, the iron oxide particle at the second half of thereaction is liable to fly. Since this flown particle is apt to stay in ashort time in the reactor, the carburization degree becomes low, and theaverage carburization degree of the product of iron carbide becomes low.Accordingly, it is preferable to regulate the gas flow velocity passingthrough fluidized bed according to the proceeding of reaction. Inaccordance with the present invention, it is possible to lower the gasflow rate to be supplied to the division room of the downstream sideless than that to be supplied to the division room of the upstream sideby means of controlling gas flow control valves (19 a˜19 f) installed ongas supply lines.

Furthermore, in the conventional process wherein the reducing reactionis partially conducted in first reactor, and the further reducing andcarburizing reaction are conducted in second reactor, it is necessary tocontrol the reduction degree of iron ore at the first reactor. For thatpurpose, said control of reduction degree may be achieved by means ofaltering the flow rate, the temperature and the composition of the gasflowing in the reactor.

But it is not easy to change the above factors because of a great dealof gas. Consequently, it is difficult to obtain a conformable andcareful control.

In accordance with the present invention, however, it is possible tocontrol uniformly the gas condition to be supplied to the division roomsexcept the final division room in plural division rooms of a firstfluidized bed reactor, besides it is possible to easily alter the flowrate, the temperature and the composition of only the gas to be suppliedto the final division room.

FIG. 6 shows that fluidized bed is partitioned into division rooms 22 c,22 d, 22 e by partition plate 26 and separation plate 24 separatingchamber 23 is installed on the upper part of the chamber. A part of gasintroduced from gas supply inlet 25 a flows into portion 23 b. Sincethis gas is mixed with gas introduced from gas supply inlet 25 b, it ispossible to make the gas component introduced into division room 22 e ofthe downstreammost different from the gas component introduced divisionrooms 22 c and 22 d of the upstream side.

FIG. 7 shows that separation plate 24 separating chamber 23 is installedfrom the top of the chamber to the bottom thereof. Separation plate 24has aperture 24 a in the lower part, and part 23 a is communicated withpart 23 b via aperture 24 a. It seems that this embodiment may achievethe same function as the embodiment shown in FIG. 6.

In case of plant having the production capacity of iron carbide of morethan 200,000 ton per year, it is preferable that the division number offluidized bed is 6˜7 and the separation number of chamber is two.

INDUSTRIAL APPLICABILITY

Since the present invention has the above constitution, the apparatusaccording to the present invention is suitable for the apparatus toefficiently produce iron carbide having the chemically stable component.

What is claimed is:
 1. A process for producing iron carbide by anapparatus having elements (a) to (e); (a) a fluidized bed located at anupper part within a fluidized bed reactor, and, (b) a chamber located ata lower part within the reactor to work as a gas header for introducinga reducing and carburizing gas; wherein the fluidized bed and thechamber are separated into upside and downside by a distribution plateon which multiple gas introducing nozzles are installed; and thefluidized bed located at an upper part of the distribution plate ispartitioned into plural division rooms which are formed in an isolatedor mazy room by a partition plate, there being at least one upstreamside reduction stage division room and at least one downstream sidecarburization stage division room being in fluid communication abovesaid partition plate within said chamber; and, (c) plural gas supplyinlets arranged on the chamber for supplying gas respectively tospecific ones of the division rooms, and, a separate gas supply linebeing connected to each of at least two inlets of said plural gas supplyinlets in order to supply reducing and carburizing gases separately tosaid at least two inlets, (d) wherein each gas supply line has a gasflow control valve for controlling a different pressure or flow rate ofthe gas supplied to the downstream side carburization stage divisionroom relative the pressure or flow rate of the gas supplied to theupstream side reduction stage division room, and comprising the step ofproviding a different pressure or flow rate in said carburization stagedivision room relative the pressure or flow rate in said reduction stagedivision room; and (e) a gas supplying apparatus through which hydrogengas and carbon-containing gas such as methane are supplied to a gascirculation loop; and further, comprising the steps for reacting grainyiron oxide charged from a side wall of the reactor with the gas in sucha manner that; the iron oxide is floated and fluidized by gas beingintroduced from the bottom portion of the reactor, and then, transferredfrom the division room of the upstream side to the division room on thedownstream side via said fluid communication above said partition plate,and finally, produced iron carbide is discharged from the final divisionroom.
 2. The process for producing iron carbide of claim 1, wherein saidchamber is separated into plural parts by a separation plate and atleast two of said plural parts each has a separate individual gas supplyinlet.
 3. The process for producing iron carbide of claim 2, wherein aseparation plate is installed at the upper part of the chamber in such amanner that only the upper part of the chamber is divided into pluralparts by said separation plate.
 4. The process for producing ironcarbide of claim 2, wherein a separation plate is installed from the topof the chamber to the bottom thereof for isolating each separation part.5. The process for producing iron carbide of claim 2, wherein aseparation plate is installed from the top of the chamber to the bottomthereof for separating the chamber into plural parts, and the separatedpart communicates with the adjacent separated part through an apertureprovided on the separation plate.
 6. The process for producing ironcarbide of claim 1, wherein the amount of water vapor contained in thegas supplied to the carburization division room is made larger than thatcontained in the gas supplied to the reduction stage division room. 7.The process for producing iron carbide of claim 6 wherein the amount ofwater vapor contained in the gas supplied to the carburization divisionroom is increased by supplying water vapor from the outside of thereactor.
 8. The process for producing iron carbide of claim 6, whereinone or more gas circulation loops having a quenching tower and a coolerwhich reduce water vapor contained in gases circulated through saidloops and wherein the amount of water vapor contained in the gassupplied to the carburization division room is increased so that thecooling operation of the quenching tower in one of said gas circulationloops is regulated so as to decrease the amount of removal of watervapor by said quenching tower and the cooling operation of the cooler ina gas circulation loop is regulated so as to decrease the amount ofremoval of water vapor by said cooler.
 9. The process for producing ironcarbide of claim 1, wherein the hydrocarbon gas or the carbon monoxidegas contained in the gas to be supplied to the carburization divisionroom is made smaller than that contained in the gas supplied to thereduction stage division room.
 10. The process for producing ironcarbide of claim 9, wherein the amount of the hydrocarbon gas or thecarbon monoxide gas contained in the gas supplied to the reduction stagedivision room of the upstream side is made larger than that contained inthe gas supplied to the carburization division room of the downstreamside by supplying hydrocarbon gas or carbon monoxide gas from theoutside of the reactor.
 11. The process for producing iron carbide ofclaim 4, wherein the gas flow rate per unit area of the gas supplied tothe carburization division room is made smaller than that of the gassupplied to the reduction stage division room.
 12. The process forproducing iron carbide of claim 1, wherein the temperature of the gassupplied to the carburization division room is made lower than that ofthe gas supplied to the reduction stage division room.
 13. The processfor producing iron carbide of claim 12, wherein a gas preheater isprovided in a gas circulation loop for heating the gas and wherein thetemperature of the gas supplied to the carburization division room ismade lower by mixing other gas having a lower temperature than the gasdischarged from the preheater in the gas circulation loop with saiddischarged gas.
 14. The process for producing iron carbide of claim 13,wherein the other gas is a part of the gas supplied to a preheater. 15.The process for producing iron carbide of claim 13, wherein the othergas is supplied from the outside of the reactor.
 16. The process forproducing iron carbide of claim 12, wherein the temperature of thefluidized bed in the division room of the downstream side is made in therange of 500-600° C.
 17. The process for producing iron carbide of claim16, wherein the temperature of the fluidized bed in a last division roomof the downstream side is made in the range of 500˜600° C. by decreasingthe temperature of only the gas supplied to said last division room. 18.The process for producing iron carbide of claim 12, wherein thetemperature of the gas supplied to the carburization division room ismade lower than that of the gas supplied to the reduction stage divisionroom in such a manner that oxygen is mixed with the gas supplied to thereduction stage division room and then, a part of combustible gascontained in said gas is partially burned in order to raise the gastemperature.
 19. The process for producing iron carbide of claim 4,wherein the concentration of hydrogen contained in the gas supplied tothe reduction stage division room is made higher than that of hydrogencontained in the gas supplied to the carburization division room. 20.The process for producing iron carbide of claim 19 wherein theconcentration of the hydrogen in the gas supplied to the reduction stagedivision room is increased by supplying hydrogen gas from the outside ofthe reactor.